I've never heard of these GEMF files. They certainly don't officially belong to OpenStreetMap.
If you want raw geodata for routing then just download it from OSM (also look at the extracts). You should read about OSM's basic elements and OSM tags for routing.
There is also an extensive wiki page about routing with OSM including a list of various online routers and offline routers, a really large list of OSM software and libraries for Android as well as for other mobile devices of which are many open source. This should be enough to get an idea where to start.